In engine-powered vehicles of all kinds, monitor devices are employed to detect the presence of various undesirable operating conditions, such as overheating of the engine, low oil pressure, low fuel and the like, and indicators are provided to give warning to the operator of such conditions. In some vehicles similar instruments are provided to indicate operating faults distinct from the engine. As, for examples, earthmoving vehicles often have an engine-powered pump which supplies pressurized fluid to hydraulic cylinders for manipulating elements of the vehicle; instruments may be present to indicate low levels of hydraulic fluid, a clogging of the hydraulic fluid filter, and so on.
The importance of the various monitored conditions usually varies as to criticality. For example, the air filter for the engine or the filter for the hydraulic fluid may gradually clog during operation of the vehicle. Such clogging should be detected and the operator warned thereof, but generally there is no need to remedy the situation until the end of the day and the vehicle returns for normal servicing and maintenance. A low fuel condition requires more immediate attention on the part of the operator. A loss of engine oil pressure or a loss of hydraulic fluid represent conditions which require immediate attention to protect the vehicle from damage.
Heretofore, monitor systems have detected the presence of undesirable conditions and then signaled the vehicle operator by means of dial indicators, indicator lamps of audible means. The efficiency of these systems is greatly dependent upon the operator's careful attention to all of the various indicators and upon his judgment as to which may call for immediate correction. In general, the more complex the vehicle, the greater is the number of operating conditions that should be monitored. At the same time, the more complex the vehicle, the less the time that the operator will have to observe the greater number of various indications since he will be more immediately concerned with direct vehicle operation.
Thus, with an increasing amount of instrumentation, a definite problem exists as to how the existence of undesirable conditions can be detected and presented to the operator without a need on his part to give greater attention, which he does not have, to such instrumentation and make value judgments relative to the criticality of undesirable conditions.
Until recently, monitor displays for use in this field, and in construction equipment, for example, have consisted of various electrical-mechanical gauges, warning lamps and warning buzzers. These arrangements provided flexibility in display formats across product lines and low individual component part cost. The disadvantage of these display formats are time consuming assembly, high assembly costs, large display areas--thereby reducing operator visibility, and large numbers of individual service parts. Recently, various monitor displays have been introduced that have reduced the assembly time, lowered assembly costs, reduced the display area--thereby providing improved operator visibility, and reduced the number of service parts. The negative aspects of these dedicated-consolidated displays are two-fold: (1) high component replacement cost, and (2) reduced flexibility across product lines.